Method and apparatus for stimulating a nerve of a patient

ABSTRACT

Single-use electrical leads for a nerve stimulator are disclosed. The leads include a status flag element such as a fuse, which is deliberately blown after use of the leads has begun to indicate that the leads are not to be reused. The nerve stimulator has a “test mode” that determines a current value for treatment, and a “therapy mode” that administers treatment with the chosen current value. If the fuse in the electrical leads is blown (not conducting), then the stimulator assumes that the leads have already been used and does not enter therapy mode, and optionally may not enter test mode. If the fuse in the electrical leads is intact (conducting), or not blown, then the stimulator assumes that the leads are as yet unused, and allows the user to enter either test mode or therapy mode. The fuse is deliberately blown after a particular amount of time spent in therapy mode. After the fuse is blown, the user may still complete the therapy mode, even though the fuse is non-conducting, although the user may not initiate another therapy mode (and optionally may not initiate another test mode) using the blown leads. Preferably the fuse is electrically isolated from the leads that contact the patient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/801,296 filed May 18, 2006, which hereby isincorporated herein in its entirety by reference thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to nerve stimulators, and moreparticularly to electrical leads for nerve stimulators and methods ofoperation thereof.

2. Description of the Related Art

Physical therapists, chiropractors, and other medical providers haveused nerve and muscle stimulation to treat a variety of ailments. Thesemedical providers have used electronic muscle stimulation (EMS) andtranscutaneous electrical nerve stimulation (TENS) as a treatment formuscle and joint rehabilitation as well as chronic pain. Urologists andobstetrician/gynecologists have used a form of TENS for pelvic floorstimulation to treat incontinence and pelvic pain. In addition, medicalproviders have used a variety of implantable and percutaneousstimulators to manage pain, to create local nerve blocks, and to treatincontinence, Parkinson's disease, and multiple sclerosis.

Transcutaneous stimulators, i.e., stimulators which do not physicallypenetrate the skin surface, are less invasive than percutaneous andimplantable stimulators. However, transcutaneous stimulators oftenrequire higher current levels than percutaneous and implantablestimulators. Higher current levels can cause irritation and discomfortwhen used for extended periods. Also, since transcutaneous stimulatorsstimulate on the skin surface, their target site usually covers a largearea. Thus, transcutaneous stimulators may not be highly effective fordirect nerve stimulation.

More typically, providers use implantable stimulators when there is aneed for direct nerve stimulation or continuous stimulation. Implantablestimulators can free a patient from the need for constant and frequentmanual treatment. However, implantable stimulators can cause milddiscomfort, and often cause more severe implant-site pain.

Percutaneous stimulators provide direct nerve stimulation without theinvasiveness of an implant. During treatment, a conducting needle isinserted to provide electrical stimulation to a target nerve. The needleis electrically connected to a controller by a series of leads, oftenbound together at one end as a cable that connects to the controller.

Leads for percutaneous stimulators may be designated for single-useonly, particularly if they have not been tested or validated formultiple uses. Since such leads should not be used multiple times, thereexists a need for electrical leads that ensure against multiple uses andfor a method of operation with these single-use leads.

BRIEF SUMMARY OF THE INVENTION

One embodiment of the present invention is a method for stimulating aposterior tibial nerve of a patient, comprising determining an initialtherapy current level for the patient; delivering a therapy current tothe nerve through a lead set expressing a “use” status, the therapycurrent being initially set to the initial therapy current level; andchanging the lead set to express a “do not use” status within apredetermined time after start of the therapy current delivering step.

Another embodiment of the present invention is a method for stimulatinga posterior tibial nerve of a patient with therapy current, comprisingactivating a stimulator, the stimulator comprising a handheld controllercoupled to a lead set having a fuse disposed therein; entering a testmode; adjusting a test current during test mode to set a final testcurrent level; exiting the test mode; entering a therapy mode when thetest mode is exited; forming an initial therapy current level from thefinal test current level; providing a therapy current through the leadset; blowing the fuse within a predetermined time after entering therapymode; and exiting the therapy mode within a predetermined time after thefuse is blown.

Another embodiment of the present invention is a posterior tibial nervestimulator comprising a controller, the controller comprising a storedprogram of digital instructions for executing a test mode to determinean initial therapy current level for the patient; executing a therapymode to deliver a therapy current to the nerve through a lead setexpressing a “use” status, the current being initially set to theinitial therapy current level; and causing the lead set to express a “donot use” status within a predetermined time after start of execution ofthe therapy mode.

Another embodiment of the present invention is an apparatus forstimulating a nerve of a patient, comprising means for determining aninitial therapy current level for the patient; means for delivering atherapy current to the nerve through a lead set expressing a “use”status, the therapy current being initially set to the initial therapycurrent level; and means for changing the lead set to express a “do notuse” status within a predetermined time after start of the therapycurrent delivering step.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic view of a nerve stimulator in use on a patient.

FIG. 2 is a perspective view of a nerve stimulator in use on a patient.

FIG. 3 is a flow chart of the operation of a nerve stimulator.

FIG. 4 is a flow chart of a current determining operation for a nervestimulator.

FIG. 5 is a flow chart of a therapy mode for a nerve stimulator.

FIG. 6 is a partial cross-sectional view of a three port single-useconnector.

FIG. 7 is an electrical schematic for a fuse implementation of thesingle-use connector of FIG. 6.

FIG. 8 is an electrical schematic for an EPROM implementation of thesingle-use connector of FIG. 6.

FIG. 9 is a plan view of a four port single-use connector.

FIG. 10 is an electrical schematic for an EPROM and fuse implementationof the single-use connector of FIG. 9.

FIG. 11 is a partial cross-sectional view of a mechanical three portsingle-use connector.

DETAILED DESCRIPTION OF THE INVENTION

Nerve and muscle stimulation may be used by medical providers to treat avariety of ailments. For instance, urinary incontinence may be treatedby stimulating the sacral nerves, which affect bladder control. One suchtreatment may be done in a percutaneous manner by inserting a fine gaugeneedle into the posterior tibial nerve just above the ankle and applyingan electrical stimulation to the needle. The tibial nerve carries theelectrical stimulation up the leg to the S3 region of the lower spinalcord. Electrical stimulation near the S3 region is effective in treatingchronic pelvic pain, fecal incontinence, nocturnal urinary frequency,interstitial cystitis symptoms of urinary frequency, urinary urgency,and urinary urge incontinence, and overactive bladder symptoms ofurinary frequency, urinary urgency and urinary urge incontinence.

An example of an electrical nerve stimulator is disclosed in U.S. Pat.No. 6,493,588 entitled “Electro-nerve stimulator systems and methods,”which issued Dec. 10, 2002 to Malaney et al., and which is herebyincorporated herein in its entirety by reference thereto. The electricalleads for the stimulator disclosed in Malaney et al. are capable ofbeing reused.

One example of suitable single-use leads rely on the conductivitybetween two particular electrical connections to determine if the leadset have been used. The two particular connections have a fuse betweenthem that conducts electricity prior to use. Once a particular set ofcriteria is met that determines that the lead set should not be reused,the fuse is deliberately blown, and the two particular connections nolonger conduct electricity from one to the other. The two particularconnections are coupled to a controller that can sense the conductivitybetween them and can also generate enough current to blow the fuse whenrequired. Preferably, the fuse and the electrical connections to thefuse are electrically isolated from the leads that deliver thestimulation current, although they may be combined with the stimulationcurrent leads if desired.

FIG. 1 shows an exemplary nerve stimulator 11 that has a set ofsingle-use electrical leads. The leads are shown in FIG. 1 as individualwires emerging from a controller 10, although it will be understood thatany or all of the leads may be packaged in a connector to simplifyconnecting or removing the leads from the controller 10.

The controller 10 may include circuitry for monitoring time andgenerating a prescribed amount of current. The current may be AC, DC, ormay alternatively be pulsed. The controller 10 may also include abattery or may alternatively use an external source of power.

As shown in FIG. 1, the controller 10 has four electrical connections orleads, although it may alternatively have more or fewer electricalconnections, such as 3, 5, 6 and so forth. In the example of FIG. 1, twoleads 16 and 18 provide a current through a portion of the patient'sbody, and the other two leads 17 and 19 are used for ensuring that theelectrical leads are used for only a single therapy session.

Lead 16 connects the controller 10 to a transcutaneous electrode 14 thatis placed in a suitable location on the exterior of the patient's body.The electrode 14 may be conductive or one or both sides, and mayoptionally have an adhesive that sticks to the patient's body.

Lead 18 connects the controller 10 to a percutaneous electrode needle 12that is inserted into the patient's body at a stimulation site 15 andconnects electrically near a nerve or bundle of nerves to be stimulated.The connector generates a voltage difference between leads 16 and 18, sothat current flows between the electrode 14 and the needle 12. Thiscurrent is denoted as arrow “i” in FIG. 1.

The remaining two leads 17 and 19 are connected to a fuse 13. Thecontroller contains circuitry that can sense whether or not fuse 13 isblown, by generating a relatively small voltage between leads 17 and 19and sensing whether or not any current is flowing through leads 17 and19. The controller also contains circuitry that can deliberately blowthe fuse 13, by generating a relatively large voltage between leads 17and 19. The voltages used in leads 17 and 19 are determined in part bythe fuse 13, and are typically low enough to not damage any tissue if itshould come in contact with the leads 17 or 19.

Illustratively, the fuse 13 and the electrical leads 16,17, 18 and 19are bundled together at the controller 10 and connect to the controller10 through a connector. A simulator 20 having an exemplary connector 22is shown in FIG. 2, along with typical a controller unit 21, leads 25and 26, an electrode 27, and a clip 28 that attaches to a needle 29.These elements are described in greater detail below. The descriptionsin the following paragraphs are merely exemplary.

The controller unit 21 may be a portable unit, with a lightweight,ergonomic, handheld design. The controller unit 21 may have electronictouch pad controls or other suitable buttons or switches for enteringdata or changing the status of the controller unit 21. For instance, thecontroller unit 21 may have raised and embossed buttons, which providetactile feedback to the user while protecting the controller unit 21from moisture, contamination, and so forth. It will be readilyunderstood by one of ordinary skill in the art that the controller mayuse any combination of buttons, switches, joysticks, levers, or anyother suitable adjustment mechanism. The controller unit 21 may have adisplay such as an LCD screen for providing operational status andvisual feedback information to the user.

The controller unit 21 includes a connection site to mate with aconnector 22. The connection site may be a one-way fit connection siteto ensure that the connector 22 for the leads cannot be plugged inbackwards. The connector 22 may be keyed to the connection site in anydesired manner, such as extended ribs, chamfers, spacing of the pins orsockets, and so forth.

The controller unit 21 contains the electronics suitable for providing acurrent for stimulating the desired nerve in the patient. Althoughspecific current settings are described in the following paragraph, itwill be understood that any suitable current scheme may used, such asdirect current (“DC”), alternating current (“AC”) with a continuouslyvarying current, AC with a pulsed current, or a combination of any ofthese. The specific current settings in the following three paragraphsare merely exemplary.

The controller unit 21 may have twenty current setting levels, rangingfrom level “0” to level “19”, representing a current range of 0 mA toapproximately 9 mA. At level “0”, the device produces 0 mA current. Atlevel “1”, the current is 0.15 mA. At level “2”, the current level is0.5 mA, and so forth. Each subsequent level represents a 0.5 mAincrease. It will be understood that other increments and levels may beused as well.

The controller unit 21 may provide a pulsed current. The frequency ofthe pulses may be fixed at 20 Hz. The pulse width may be 200microseconds. The pulse waveform may be square. It will be understoodthat other suitable frequencies, pulse widths, and waveforms may be usedas well, and may optionally be adjustable.

The internal resistance of the controller unit 21 may be varied by thecontroller unit 21 from 500 to 4000 Ohms in order to provide the desiredcurrent. This range is merely exemplary, and other suitable ranges maybe used as well.

The following paragraphs describe the buttons on the controller unit 21in greater detail. These descriptions are merely exemplary.

The controller unit 21 may have a “power” button that turns the power onor off. To turn the power on or off, the user may be required to depressthe power button for an extended period, such as approximately twoseconds, to protect the controller unit 21 from inadvertent statuschanges.

The controller may have a “test” button, which begins “test mode”. “Testmode” is described in greater detail later in this document. Uponentering test mode, the default current setting may be “0”, or 0 mA. Atthe completion of the test mode, the final current setting may be thebaseline setting in “therapy mode”, which is also described in greaterdetail later in this document. To activate test mode, the user may berequired to depress the test mode button for an extended period, such asapproximately two seconds. This may protect the controller unit 21 frominadvertent status changes.

The controller unit 21 may have a “therapy” button, which begins“therapy mode”. The default current setting for therapy mode may be thefinal current setting in test mode. However, the current adjustmentbutton (described below) may be used to increase or decrease the levelat any time. To activate therapy mode, the user may be required todepress the therapy mode button for an extended period, such asapproximately two seconds. This may protect the controller unit 21 frominadvertent status changes.

The controller unit 21 may have a “stop” button that stops the flow ofcurrent in test or therapy mode. If treatment is stopped or interruptedduring therapy mode, the remaining therapy mode time may be displayed.Once stopped, the treatment session may need to be restarted, beginningwith test mode.

Finally, the controller unit 21 may have a “current adjustment” button,which increases or decreases current. The current may be adjustable inboth test and therapy modes.

The following seven paragraphs describe the status screen on thecontroller unit 21 in greater detail, which may have icons and/oralpha-numeric characters that provide operational feedback. Thesedescriptions are merely exemplary.

The controller unit 21 may have a “battery level” icon. The number ofhorizontal lines displayed in the battery level icon may represent theremaining battery life. Seven horizontal lines may indicate a fullycharged battery whereas one horizontal line may indicate that thebattery is nearly empty. A flashing battery level icon may signal that areplacement battery may be needed. In addition, the controller unit 21may emit a periodic beep when the battery is nearly empty, such as whenonly one line is displayed in the battery level icon. The controllerunit 21 may be designed to prohibit the start of test mode if there isinsufficient battery life remaining to complete the treatment.

The controller unit 21 may have a “lead wire status” icon, which mayindicate the functional status of the lead wire. The icon may flash if anew lead wire is required.

The controller unit 21 may have an “inactive current” icon, which mayindicate that current is not flowing through the lead set. This icon maysignal that the user should check the security of the lead connector,the adherence of the surface electrode, and the placement of the needleelectrode clip.

The controller unit 21 may have an “active current” icon, which mayindicate that current is actively flowing through the lead set.

The controller unit 21 may have a “service required” icon. If a fault isdetected, therapy mode may end and the service required icon may appearon the screen.

The controller unit 21 may have a “treatment status” portion of thescreen. During test mode, the word “TEST” may appear on the screen. Oncetherapy mode is started, a countdown timer may appear in a portion ofthe display. This timer may indicate how much time is left in thetherapy session. Upon completion of therapy, the word “END” may flash onthe screen until shutdown.

Finally, the controller unit 21 may have a “current setting” portion ofthe screen, which may display the selected current setting. The currentmay be adjustable in both test and therapy modes.

The leads transfers the electrical current from the controller unit 21to the tibial nerve and may include one or more lead sets such as leadset 23, one or more percutaneous electrodes such as needle electrode 29,one or more surface electrodes such as electrode 27, and an optionalalcohol pad (not shown). The following description of these elements ismerely exemplary.

The components of the lead set 23 create the non-sterile circuitinterface between the controller unit 21 and the patient. A one-way fitconnector 22 is attached to the proximal end of the lead wire 23. Thedistal end of the lead wire may be split into individual wires 25 and26, with the split occurring at a fork 24. One wire 25 may be attachedto an adhesive-backed surface electrode 27; the other wire 26 may beattached to a needle electrode clip 28.

The needle electrode clip 28 clips to the needle electrode 29. Theneedle electrode 29 illustratively is a 34 gauge solid stainless steelneedle, which may be packaged within a plastic guide tube with stopplug. Each needle electrode 29 may be supplied sterile (ethylene oxide)in an individual peel-open package.

The alcohol pad may be prepackaged to clean the needle electrodeinsertion site.

The following paragraphs describe a preferred set of instructions foruse of the stimulator. These instructions are merely exemplary. Anysuitable instructions may be used.

Percutaneous tibial nerve stimulation (PTNS) therapy involves placingthe needle electrode 29 into the lower, inner aspect of either legslightly cephalad to the medial malleolus. The surface electrode 27 isplaced over the medial aspect of the calcaneous on the same leg. Thelead set 23 first is plugged into the stimulator 21, and then the needleelectrode clip 28 is clipped to the needle electrode 29. The stimulator21 produces an adjustable electrical pulse that travels to the sacralnerve plexus via the tibial nerve. Among other functions, the sacralnerve plexus regulates bladder and pelvic floor function.

The patient is typically treated once per week for 30 minutes for aperiod of 12 weeks. No decision to discontinue treatment should be madeuntil the patient completes the 12 treatments. For patients respondingto treatment, the time between treatment sessions may be slowlyincreased after the initial 12 treatments, with the patient closelymonitored for the return of symptoms. If symptoms reappear or increasein severity, the patient's treatment schedule should revert to the lastpreviously effective treatment schedule. The treatment length of 30minutes and period of 12 weeks are merely exemplary, and any suitablelength and period may be used.

The following section describes a preferred treatment protocol 30 foreach treatment session, shown as flow charts in FIGS. 3-5. Because theprotocol is lengthy, it is divided into sections numbered 1-8, withappropriately lettered subsections. The described protocol is merelyexemplary. Alternatively, any suitable protocol may be used.

1. Check Battery Level (Block 31)

Before beginning any treatment session, it is advisable to check thebattery level. To check the battery level, turn on the stimulator bypressing and holding the power button for approximately 2 seconds. Anaudible tone will sound and icons will appear on the screen. Batteryreplacement is recommended when there is only one line remaining in thebattery level icon. To conserve battery power, the stimulator may beturned off during patient preparation. Note that the system is designedto prohibit the start of Test mode if there is insufficient battery liferemaining to complete the treatment.

2. Insert the Needle Electrode (Block 32)

Locate the insertion site for the needle electrode by identifying thelocation on the lower inner aspect of either leg that is approximatelythree fingerbreadths (5 cm or 2 inches) cephalad to the medial malleolusand approximately one fingerbreadth (2 cm or ¾ inch) posterior to thetibia.

To prepare the needle electrode insertion site, open the lead setpackaging. Remove and open the alcohol pad. Use the alcohol pad to cleanthe skin area surrounding the identified insertion site.

Place the patient in a comfortable position, supine or sitting, for easyaccess to the insertion site; for example, the patient may sit with thesoles of the feet together and knees abducted and flexed. Open thesterile needle electrode package and remove the needle electrode/guidetube assembly.

Place the needle electrode/guide tube assembly over the identified andcleaned insertion site in a position that creates a 60-degree anglebetween the needle electrode and the ankle. Remove the stop plug in theguide tube to release the needle electrode.

Gently tap the needle electrode head to pierce the skin. Once the needleelectrode has penetrated the skin, remove the guide tube and advance theneedle electrode using a rotating motion to facilitate entry. Note: itis preferable to maintain a 60-degree angle with the needle electrodewhile advancing it in a path that is parallel to the tibia. Whenappropriately inserted, about half of the tip of the needle electrodewill be inserted in the leg, with about 2 cm (¾ inch) left exposed.

3. Connect Lead Wire to the Stimulator (Block 33)

Plug the one-way fit connector of the lead set into the stimulator'sconnection site. Verify that the one-way fit connector is insertedcorrectly.

4. Attach the Surface Electrode (Block 34)

Remove the adhesive backing from the surface electrode.

Place the surface electrode near the medial aspect of the calcaneus onthe same leg as the needle electrode insertion.

5. Attach Needle Electrode Clip (Block 35)

Depress the plunger on the needle electrode clip to expose theconnection hook at the tip. Loop the connection hook around the needleelectrode and release.

6. Determine Current Setting for Therapy (Block 36)

Turn on the stimulator by pressing and holding the power button forapproximately 2 seconds (FIG. 4, block 41). An audible tone will soundand symbols will appear on the screen. Note that if the lead wire statusicon is blinking, ensure that the lead set connector is secure in thestimulator's connection site.

Enter test mode by pressing and holding the test button forapproximately 2 seconds (block 42). The default setting for test mode islevel 0 (0 mA current). Note that if the inactive current icon appears,current is not flowing through the lead set. Check the security of thelead wire connector, the adherence of the surface electrode, and theplacement of the needle electrode clip.

Using the current adjustment button, slowly increase the current (block43) while observing the patient's foot for a response (blocks 44 and45). Patient response is generally a toe flex or fan, or an extension ofthe entire foot.

Once a patient response is observed, reduce current setting by one level(block 46) to complete test mode (block 47), and begin therapy mode(block 48).

If the incremental adjustment of amplitude fails to elicit toe flex orfan, press the stop button and reposition the needle electrode slightly.Re-enter test mode using the preceding procedure.

If repositioning the needle electrode and repeating the current step-upprocedure fails to elicit patient response, discard the needleelectrode. Open the second needle electrode included with the lead setand repeat the procedure on the other leg.

7. Conduct therapy (Block 37)

After completing test mode, therapy mode can be entered by either (i)pressing the stop button to end test mode and then pressing the therapybutton to start therapy mode; or (ii) pressing the therapy button whilethe test mode is still active. Note that the test mode is a prerequisiteto therapy mode.

For optimal treatment, the default current setting for therapy modeshould be the final current setting in test mode. However, the currentadjustment button can be used to increase or decrease the current levelat any time during Therapy mode.

Therapy mode time is automatically set for 30 minutes.

When the therapy time has elapsed, therapy mode automatically ends thecurrent becomes inactive (block 57) and the stimulator emits a series ofthree beeps.

8. Complete Treatment Session (Block 38)

Turn off the stimulator by holding down the power button forapproximately 2 seconds.

Remove the needle electrode clip from the needle electrode.

Using a smooth, fluid motion, quickly remove the needle electrode andsurface electrode from the leg. If bleeding occurs, apply slightpressure and bandage.

Disconnect the lead set from the stimulator and properly dispose of thelead set components. The treatment session is now complete.

Treatments as described above are preferably administered periodicallyover a prescribed length of time. For instance, the treatments mayinclude 12 sessions, typically once per week. After the initial 12treatments, the time between treatments may slowly increase, with thepatient closely monitored for the return of symptoms. If symptomsreappear or increase in severity, the patient's treatment schedule mayrevert to the last previously effective treatment schedule.

It will be beneficial to reiterate and summarize several of the pointsfrom the exemplary protocol above, especially “test mode” and “therapymode.” In general terms, “test mode” is used to determine a currentvalue for treatment, and “therapy mode” administers treatment with thechosen current value. More specific aspects of these two modes arepresented in the following paragraphs.

Refer to FIG. 5. If the fuse in the electrical leads is blown, that is,not conducting (block 51 yes), then the controller assumes that theleads have already been used (block 58). The controller produces asuitable signal, such as an audible beep or a visual cue on its displayindicating that the leads need to be replaced. The controller does notenter test mode or therapy mode at this point. Alternatively, thecontroller may enter test mode but not therapy mode.

If the fuse in the electrical leads is intact (conducting), or notblown, then the controller assumes that the leads are as yet unused, andallows the user to enter either test mode or therapy mode.

Refer now to FIG. 4. Once inside test mode (block 42), the user maymanually step up the current (blocks 43, 44 and 45) until the patient'sfoot shows a response, such as a movement. Once a response is seen, theuser may manually decrease the current by one increment (block 46) to avalue that is to be used as a default in therapy mode. Test mode lastsfor a particular amount of time, such as five minutes, then shuts off.The user can also manually exit test mode before the particular timeexpires. The user can exit and enter test mode an unlimited number oftimes, as long as the fuse in the leads is conducting. Entering orexiting test mode does not cause the controller to deliberately blow thefuse. Alternatively, the fuse may be blown after a predetermined numberof test mode reentries.

Refer again to FIG. 5. Once a default current value is determined fromtest mode (block 53; see also block 48 in FIG. 4) the user then beginstherapy mode. The current may be increased or decreased at any time intherapy mode, although preferably the current remains fairly close tothe default value for the full extent of therapy mode. Therapy mode maylast for a fixed amount of time, although the user can exit at any time.Unlike test mode, therapy mode triggers the deliberate blowing of thefuse in the leads (block 55) thereby ensuring that the leads are notreused after the therapy mode ends. The fuse may be blown after aparticular amount of time spent in therapy mode (block 54) such as oneminute, two minutes, five minutes or any other suitable time interval.After the fuse is deliberately blown, the user may still complete thetherapy mode (block 56) even though the fuse is non-conducting, althoughthe user may not initiate another test mode or therapy mode using theblown leads. Alternatively, the user may initiate a test mode but not atherapy mode using the blown leads. Once therapy mode ends, the currentis set to zero (block 57).

The nerve stimulation system is effective not only for the treatment ofchronic pelvic pain, fecal incontinence, nocturnal urinary frequency,interstitial cystitis symptoms of urinary frequency, urinary urgency,and urinary urge incontinence, and overactive bladder symptoms ofurinary frequency, urinary urgency and urinary urge incontinence, butmay also be effective for both nerve and muscle stimulation to treatother numerous conditions, including, for example, muscle and jointrehabilitation, chronic pain, Parkinson's disease, obesity, and multiplesclerosis. While many of these other conditions may use different nervepathways than the one described herein, the nerve stimulator may be usedin a similar manner for any suitable nerve pathway in the body. Inaddition, the system may be used to manage pain and create local nerveblocks, as well as in any other application in which it is desirable toprovide electrical nerve and/or muscle stimulation.

Although a fuse is a simple and effective way to indicate whether thelead set has been used, other means may be used as well. Generally, thelead set may contain a “status flag” element to indicate whether thelead set has been used. The status flag element is reset by default at“use,” and once a particular set of criteria is met that determines thatthe leads should not be reused, the status flag element is set at “donot use.” The controller senses the lead set status as indicated by thestatus flag element, and is also capable of setting the status flagelement at “do not use” when required.

A variety of electrical and mechanical techniques for implementing astatus flag element are described in U.S. patent application Ser. No.10/492,578 filed Sep. 13, 2004, which hereby is incorporated herein inits entirety by reference thereto. Illustrative techniques include thefollowing.

FIGS. 6-11 illustrate a variety of possible techniques which may beimplemented in a connector for ensuring single use. As shown in FIG. 6,a connector 100 includes two ports A and B corresponding to stimulationcurrent lead wires 102 and 104 (also designated by correspondingreference letters A and B). FIG. 7 shows one type of status flag,illustratively a fuse 120, which may be blown and subsequently sensed bya controller (not shown) through a third port C to indicate that thelead set has been used. Alternatively, as illustrated in FIG. 8, theconnector 100 may include another type of status flag, illustratively asingle wire serial read/write non-volatile erasable, programmable readonly memory (EPROM) 122, which may be programmed and subsequently readby a controller through port C to indicate that the lead set has beenused. Other types of memory may be used as well, including single andmultiple bit memory and Flash memory. Other types of devices may be usedas well, including digital potentiometers.

FIGS. 9 and 10 show a connector 106 that incorporates both a serialread/write non-volatile EPROM 123 and a fuse 120. The EPROM 123 may beprogrammed with information to instruct a controller to burn out thefuse 120 after a preselected time period, or to generate a current spiketo burn out the fuse 120 after expiration of a preselected time period.Other components shown in FIG. 10 include a resister 124 and a Zenerdiode 126.

FIG. 11 shows an illustrative mechanical mechanism that may be employed,in which a pin 128 is biased within port C. In operation, upon insertionof the connector 112 into a corresponding receptacle, the mechanism isactuated to release the biased pin 128. Upon removal of the connector112 from the female receptacle, the released pin 128 prevents theconnector from being reinserted into the female receptacle to preventreuse.

The transcutaneous electrode and the percutaneous electrode may beimplemented in any desired manner. While FIG. 2 shows a needle clip 28,for example, the lead may terminate in a needle without the interveningclip, or equivalents such as conductive tape may be used. An example ofa suitable conductive tape is described in U.S. patent application Ser.No. 10/492,578 filed Sep. 13, 2004, which hereby is incorporated hereinin its entirety by reference thereto. As described therein, a suitabletape member may have various layers sandwiched together, including anon-electrically conductive top layer, an intermediate electricallyconductive foil layer, and a bottom electrically conductive adhesivelayer. The opposing ends of the tape member are folded over onto eachother and over the terminal end of the percutaneous needle electrode.

The description of the invention and its applications as set forthherein is illustrative and is not intended to limit the scope of theinvention. Variations and modifications of the embodiments disclosedherein are possible, and practical alternatives to and equivalents ofthe various elements of the embodiments would be understood to those ofordinary skill in the art upon study of this patent document. These andother variations and modifications of the embodiments disclosed hereinmay be made without departing from the scope and spirit of theinvention.

1. A method for stimulating a posterior tibial nerve of a patient,comprising: determining an initial therapy current level for thepatient; delivering a therapy current to the nerve through a lead setexpressing a “use” status, the therapy current being initially set tothe initial therapy current level; and changing the lead set to expressa “do not use” status within a predetermined time after start of thetherapy current delivering step.
 2. The method of claim 1, wherein thetherapy current delivering step extends beyond the changing step.
 3. Themethod of claim 1, wherein the initial therapy current level determiningstep comprises: alternately increasing a test current and observing thepatient for a physical response; observing the physical response fromthe patient; decreasing the test current to a final test current level;and setting the initial therapy current level equal to the final testcurrent level.
 4. The method of claim 3, wherein the test current isincreased and decreased in increments of 0.5 mA.
 5. A method ofoperating a nerve stimulator having a lead set, comprising: executing atest mode to determine an initial therapy current level for the patient;executing a therapy mode to deliver a therapy current to the nervethrough the lead set, the current being initially set to the initialtherapy current level, and the lead set comprising a status flag elementhaving a “use” status; and setting the status flag element in the leadset within a predetermined time after start of execution of the therapymode.
 6. The method of claim 5, wherein: the status flag element is afuse; and the setting step comprises blowing the fuse.
 7. The method ofclaim 6, wherein the fuse is not in the electrical pathway of thecurrent.
 8. The method of claim 5, wherein the therapy mode extendsbeyond the setting step.
 9. The method of claim 8, wherein the therapymode lasts for about 30 minutes.
 10. A method for stimulating aposterior tibial nerve of a patient with therapy current, comprising:activating a stimulator, the stimulator comprising a handheld controllercoupled to a lead set having a fuse disposed therein; entering a testmode; adjusting a test current during test mode to set a final testcurrent level; exiting the test mode; entering a therapy mode when thetest mode is exited; forming an initial therapy current level from thefinal test current level; providing a therapy current through the leadset; blowing the fuse within a predetermined time after entering therapymode; and exiting the therapy mode within a predetermined time after thefuse is blown.
 11. The method of claim 10, wherein the test currentadjustment during test mode comprises: increasing the test current froman initial test current level of zero; observing the patient whileincreasing the test current; observing a patient response; anddecreasing the test current to the final test current level when thepatient response is observed.
 12. The method of claim 10, wherein thetherapy current is initially set to the initial therapy current leveland is adjustable throughout the therapy mode.
 13. A posterior tibialnerve stimulator comprising a controller, the controller comprising astored program of digital instructions for: executing a test mode todetermine an initial therapy current level for the patient; executing atherapy mode to deliver a therapy current to the nerve through a leadset expressing a “use” status, the current being initially set to theinitial therapy current level; and causing the lead set to express a “donot use” status within a predetermined time after start of execution ofthe therapy mode.
 14. The nerve stimulator of claim 13, furthercomprising the lead set coupled to the controller, the lead setcomprising a status flag element.
 15. An apparatus for stimulating anerve of a patient, comprising: means for determining an initial therapycurrent level for the patient; means for delivering a therapy current tothe nerve through a lead set expressing a “use” status, the therapycurrent being initially set to the initial therapy current level; andmeans for changing the lead set to express a “do not use” status withina predetermined time after start of the therapy current delivering step.